Microwave oven capable of preventing overcurrent of a microswitch for controlling a DC power source

ABSTRACT

A microwave oven has a case forming a cooking chamber, a door for opening/closing said chamber, a high voltage transformer for generating a high voltage, and a magnetron for generating microwaves driven by the high voltage outputted from the high voltage transformer. The microwave oven further includes a microswitch serving as a detector for detecting opening/closing of the cooking chamber; a control device for outputting a driving signal corresponding to the detected opening/closing of the chamber, and an opening/closing device for controlling a power source supplying power to the high voltage transformer according to reception of the driving signal.

TECHNICAL FIELD

The present invention relates to a microwave oven, and more particularlyto a microwave oven capable of preventing overcurrent of a microswitchfor controlling a DC power source, which is capable of being preventedfrom holding the previous status of contacts in a microswitch caused bythe large amounts of current which are remaining when usig directcurrent.

BACKGROUND ART

FIG. 1 shows a microwave oven for heating/cooking food using microwaves.The microwave oven contains a case 20 for forming a cooking chamber 22,a door 21 for opening/closing the cooking chamber 22, a tray 24 beinginstalled in the cooking chamber 22, and a panel 25 for controllingoperations of the microwave oven.

FIG. 2 is a partial cutaway view of FIG. 1. A pair of latch hooks 28 a,28 b are installed in the door 21, and catch openings 27 a, 27 b areformed corresponding to each latch hook 28 a, 28 b at a front plate 26of the case 20. If the door 21 is pushed shut, the latch hooks 28 a, 28b will engage the catch openings 27 a, 27 b to hold the door 21 shut.

At the back side of the panel 25 is provided a device chamber (notshown). In the device chamber are installed a magnetron for generatingmicrowaves and a high voltage transformer HVT for generating a highvoltage supplied to the magnetron, and so on. In supplying an AC powerto the high voltage transformer HVT, this high voltage transformer HVTgenerates a predetermined high voltage to drive the magnetron. Then, themagnetron radiates microwaves of about 2,450 MHz frequency to heat/cookfood.

As shown in FIG. 2, microswitches MS1, MS2, MS3 are installed at theback side of the front plate 26 of the case 20. FIGS. 3a, and 3 b areschematic diagrams and symbols of each microswitch MS1, MS2, MS3,respectively. The microswitches MS1, MS2, MS3 have a slight interval atthe contacts, and a mechanism of a snap action. The microswitches MS1,MS2, MS3 have a contact mechanism to open/close by the determinedoperation and force in a sealing case, and is a small switch forarranging a pushing mechanism of the actuator switch located on theoutside of the case. That is, the microswitch is one of the contact typedetectors, which detects something contacted according to releasing theinside contacts when something 6 closes to a push button 1, and beginsto push the push button 1, and applies more than a predetermined force Fto the push button 1. In FIG. 3, the reference numeral 2 is a movablespring, and the reference numeral 3 is a movable contact. The referencenumeral 4 is a fixed contact b, and the reference numeral 5 is a fixedcontact a. COM, NO, and NC are a common terminal, a normally openterminal, and a normally closed terminal, respectively. In FIG. 3b, thecontact a 7 is a point of contact which conducts first when themicroswitch is operated, and which connects the common terminal COM intothe normally open terminal NO. The contact b 7 is a point of contactwhich conducts when the microswitch is not operated, and which connectsthe common terminal COM into the normally close terminal NC.

The microswitches MS1, MS2, MS3 have each operating button 31, 32, 33,respectively. At the back side of the front plate 26 are installed apair of movable members 29 a, 29 b to adjoin the catch openings 27 a, 27b. Then, the movable members 29 a, 29 b are fixed for pivoting by eachpin 23 a, 23 b, and are fixed elastically by each spring 41 a, 41 b.

In FIG. 2, if the door 21 is pushed close, the microswitches MS1, MS2,MS3 are operated by the latch hooks 28 a, 28 b which are inserted in thecatch openings 27 a, 27 b. That is, when the movable members 29 a, 29 bare pushed by each latch hook 28 a, 28 b, the movable members 29 a, 29 bare rotated against the elasticity of the springs 41 a, 41 b. Therefore,the operating button 31 is pushed by the upper movable members 29 a, andthe operating buttons 32, 33 are pushed by the lower movable members 29b, respectively.

Meanwhile, since the conventional microwave oven has been made to beoperated using the AC common power source of 110V/220V for supplyinghigh alternating current, we cannot use the microwave oven in a placewhere alternating current is not available.

To overcome the above described problem, an AC/DC type microwave ovenhas been developed, and has been comprised as shown in FIG. 4. In FIG.4, An AC/DC type microwave oven comprises an AC driving load 30, a DCdriving load and DC/AC converting part 40, and a microwave oscillator50. The AC driving load 30 is driven by an AC input power. The DCdriving load and DC/AC converting part 40 includes the DC driving loadbeing driven by a DC input power, and the DC/AC converter converting theDC input power into an AC power. The microwave oscillator 50 is suppliedby only one of the AC input power or the DC/AC power converted by aDC/AC converter, and generates microwaves.

The AC driving load 30 is driven by alternating current, which includesa lamp and a fan motor, etc., which are connected to the AC powersource. A power switch (not shown) to determine the supplying status ofAC is connected to the AC power source. The DC driving load being drivenby direct current, which includes a lamp and a fan motor, etc., whichare connected to the DC power source. A power switch (not shown) todetermine the supplying status of DC is connected to the DC powersource. The direct current forms a differentiated DC circuit netdiscriminated as an AC circuit net. Then, direct current is connected tothe input side of the DC/AC converting part 40 which suppliesalternating current. The microwave oscillating part 50 includes a highvoltage transformer HVT which receives the AC power, a high voltagecondenser HVC, a high voltage diode HVD, and a magnetron MGT. Theoperation of the microwave oscillating part 50 is described the same wayas shown in FIG. 1.

Therefore, according as the AC power source supplies alternating currentto the AC driving load 30, and the DC power source supplies directcurrent to the DC driving load and DC/AC converting part 40,respectively, the conventional AC/DC type microwave oven is operated.

In the above-described AC/DC type microwave oven, the DC driving loadand DC/AC converting part 40 is designed for the user to use the AC/DCtype microwave oven out-of-doors, using the power source of anautomobile battery. Generally, however, the common AC power sourcesupplies small amounts of current within 15A, but the battery of theautomobile using DC supplies large amounts of current from 50A to 70A.

If the microwave oven is operated by using the automobile battery, themicroswitches MS1, MS2 have the possibility of a faulty operation.

That is, in case the large amounts of current is supplied through themicroswitches MS1, MS2, the contact of the microswitches MS1, MS2 canremain in there contacting status. When the user pulls the door 21 sothat the cooking chamber is open, the operating buttons 31, 32 of themicroswitches MS1, MS2 can remain in their depressed status. Accordingas the primary switch PD and secondary switch SD of the DC driving loadand DC/AC converting part 40 are held in their closed status, and thencurrent is supplied to the DC driving load and DC/AC converting part 40,so the AC/DC type microwave oven has the problem of encountering amalfunction.

DISCLOSURE OF INVENTION

The present invention has been made to overcome the problems withmicrowave ovens described in the foregoing paragraphs, and accordinglyit is the first objective of the present invention to provide amicrowave oven capable of preventing overcurrent of a microswitch forcontrolling a DC power source.

It is the second objective of the present invention to provide amicrowave oven for heating/cooking food safely by preventing overcurrentof a microswitch for controlling a DC power source.

To achieve the above objectives, the present invention provides amicrowave oven capable of preventing overcurrent of a microswitch forcontrolling a DC power source. In a microwave oven having a case forminga cooking chamber, a door for opening/closing the chamber, a highvoltage transformer for generating a high voltage, and a magnetron forgenerating microwaves driven by the high voltage being outputted fromthe high voltage transformer, a microwave oven comprising: means fordetecting opening/closing of the door; means for controlling foroutputting a driving signal corresponding to the detected result; andmeans for opening/closing for controlling a power source supplied to thehigh voltage transformer according to receiving the driving signal.

The means for detecting is a microswitch which is a detector fordetecting the openinig/closing of the door.

The means for opening/closing is an electromagnetic relay forcontrolling an opening/closing of an input power source to open/close acontact according to the driving signal, wherein the relay is anelectromagnetic relay for controlling a supply of large amounts ofcurrent from 50A to 70A.

To achieve the above objectives, the present invention provides aninterlock device of a microwave oven. In a microwave oven having a caseforming a cooking chamber, a door for opening/closing the chamber, ahigh voltage transformer for generating a high voltage, and a magnetronfor generating microwaves driven by the high voltage being outputtedfrom the high voltage transformer, an interlocking device of a microwaveoven comprising: microswitches for detecting opening/closing of thedoor; microcomputer for outputting a driving signal corresponding to thedetected result; and a relay for opening/closing for controlling a powersource supplied to the high voltage transformer according to receivingthe driving signal.

The relay is an electromagnetic relay for controlling a supply of largeamounts of current from 50A to 70A.

To achieve the above objectives, the present invention provides amicrowave oven capable of preventing overcurrent of a microswitch forcontrolling a DC power source. In a microwave oven using microwaves, themicrowave oven comprising: a DC circuit part for converting directcurrent supplied by a DC input power source into alternating current,and for supplying the converted alternating current; an opening/closingmeans for connecting between the DC input power source and the DCcircuit part; a current dividing means being connected to the means foropening/closing, and for dividing a part of current supplied by themeans for opening/closing when the means for opening/closing is switchedon; and a microwave oscillating means for being driven by an outputvoltage of the high voltage transformer, and for generating microwaves.

The current dividing means is a relay connected to the opening/closingmeans in parallel. The present invention further comprises resistors forbeing connected to the opening/closing means and/or the relay currentdividing means in series, respectively, and for regulating each rate ofcurrent through the opening/closing means and the relay, respectively.

To achieve the above objectives, the present invention provides a devicefor preventing overcurrent of a microswitch comprising: a microswitchfor opening/closing the connection between DC input power source and aDC circuit part being supplied direct current; and a current dividingmeans being connected to the microswitch in parallel, and for dividing apart of current through the microswitch when the microswitch is switchedon.

According to the present invention, a microwave oven is capable ofpreventing overcurrent of a microswitch by using a relay, and so on. Amicrowave oven can be heating/cooking food safely according to beingprevented from a holding of the previous status of contacts in amicroswitch by preventing overcurrent of a microswitch for controlling aDC power source.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objective and other advantages of the present invention willbecome more apparent by being described in detail in a preferredembodiment thereof with reference to the attached drawings, in which:

FIG. 1 is a cutaway view of a conventional microwave oven;

FIG. 2 is a partial cutaway view of FIG. 1 for explaining a microswitchand the operation of the opening/closing of the conventional microwaveoven;

FIGS. 3a and 3 b are a schematic diagram and symbols of the microswitch,respectively;

FIG. 4 is a block diagram of an AC/DC type microwave oven developedherein;

FIG. 5 is a block diagram of a microwave oven capable of preventingovercurrent of a microswitch for controlling a DC power source accordingto the first embodiment of the present invention;

FIG. 6 is a block diagram of a microwave oven capable of preventingovercurrent of a microswitch for controlling a DC power source accordingto the second embodiment of the present invention;

FIGS. 7a and 7 b are a block diagram and symbols of relays of FIGS. 5and 6, respectively;

FIG. 8 is a schematic diagram of a microwave oven capable of preventingovercurrent of a microswitch for controlling a DC power source accordingto the first embodiment of the present invention; and

FIG. 9 is a schematic diagram of a microwave oven capable of preventingovercurrent of a microswitch for controlling a DC power source accordingto the second embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will become more apparent by describing in detailin a preferred embodiment thereof with reference to the attacheddrawings. If the parts of the present invention are the same as aconventional microwave oven as shown on FIGS. 1 and 3, the illustrationcan be abbreviated, and can be cited using the same reference numerals.

FIG. 5 is a block diagram of a microwave oven capable of preventingovercurrent of a microswitch for controlling a DC power source accordingto the first embodiment of the present invention. In a microwave ovenhaving a case forming a cooking chamber, a door for opening/closing thechamber, a high voltage transformer for generating a high voltage, and amagnetron for generating microwaves driven by the high voltage beingoutputted from the high voltage transformer, this microwave ovenaccording to the first embodiment comprising: microswitches 100, 110 fordetecting the opening/closing of the door; microcomputer 150 forcontrolling being outputted a driving signal corresponding to thedetected result; and a relay 220 for opening/closing for controlling apower source supplied to the high voltage transformer according toreceiving the driving signal; a DC/AC converter 300 for convertingdirect current supplied by a DC input power source into alternatingcurrent, and for supplying to the high voltage transformer; and amicrowave oscillator 400 being driven by an output voltage of the highvoltage transformer, and for generating microwaves. The relay 220 is anelectrical relay which is opening/closing a supply of input power byopening/closing contacts according to the driving signal, andopens/closes a supply of large amounts of current from 50A to 70A.

FIG. 8 is a schematic diagram of a microwave oven capable of preventingovercurrent of a microswitch for controlling a DC power source accordingto the first embodiment of the present invention. This microwave ovenaccording to the first embodiment comprises an AC circuit part 500, a DCcircuit part 600, and a microwave oscillating part 400. The AC circuitpart 500 supplies a high voltage transformer 410 with alternatingcurrent by an AC input power source, and the DC circuit part 600supplies to the high voltage transformer 410 which converts alternatingcurrent after converting direct current supplied by a DC input powersource into alternating current, and the microwave oscillating part 400generates microwaves by means of the output voltage of the high voltagetransformer 410. The DC circuit part 600 uses relays 221, 222 foropening/closing a DC input power source. The opening/closing of the dooris detected by microswitches 100, 110, microcomputer produces thedriving signal to the relays 221, 222 corresponding to the detectedresult, so the relays 221, 222 can open/close the DC input power source.

The microwave oven contains microswitches MS1, MS2, MS3 for controllingoperations of each first switches PA, PD, each second switches SA, SD,and each monitor switches MA, MD. Substantially, the first microswitchMS1 operates along with the first switches PA, PD, the secondmicroswitch MS2 operates along with the second switches SA, SD, and thethird microswitch MS3 operates along with the monitor switches MA, MD,respectively.

The high voltage transformer 410 contains many coils 411, 412, 413, 414,and is driven by the AC circuit part 500 or the DC circuit part 600 togenerate a high voltage of about 2,000V.

The AC circuit part 500 contains the first lamp L1, the first fan motorFM1, and the first and second switches PA, SA and the monitor switch MAfor controlling an AC power.

If the first and second switches PA, SA are switched on and the monitorswitch MA is switched off, the first lamp L1 and the first fan motor FM1are driven, and the AC input power source supplies alternating currentto the high voltage transformer 410 simultaneously. Then, the highvoltage transformer 410 generates a high voltage, and a magnetron MGTgenerates microwaves by means of the high voltage.

The DC circuit part 600 contains the second lamp L2, the second fanmotor FM2, a DC/AC converter 300 for converting direct current suppliedby DC input power source into alternating current, and the relays 221,222 along with a monitor switch MD for controlling a DC power.

The DC/AC converter 300 contains a commutator 330, a commutator motor Mfor rotating the commutator 330, and two pairs of brushes 321, 322, 323,324 being contacted to the outer circle of the commutator 330. Two pairsof brushes 321, 322, 323, 324 consist of one of input brushes 321, 323being connected to direct current, and one of output brushes 322, 324being connected to the high voltage transformer 410. The pair of inputbrushes 321, 323 is contacted to the outer circle of the commutator 330,and supplies direct current to the commutator 330. The pair of outputbrushes 322, 324 is contacted to the outer circle of the commutator 330and converts direct current supplied by the input brushes 321, 323 intoalternating current, when the commutator 330 is rotated.

As shown in FIG. 2, microswitches MS1, MS2, MS3 are installed at theback side of the front plate 26 of the case 20. The microswitches MS1,MS2, MS3 have each operating button 31, 32, 33, respectively. At theback side of the front plate 26 is installed a pair of movable members29 a, 29 b to adjoin the catch openings 27 a, 27 b. Then, the movablemembers 29 a, 29 b are fixed for pivoting by each pin 23 a, 23 b, andare fixed elastically by each spring 41 a, 41 b.

If the door 21 is pushed close, the microswitches MS1, MS2, MS3 areoperated by the latch hooks 28 a, 28 b which are inserted in the catchopenings 27 a, 27 b. That is, when the movable members 29 a, 29 b arepushed by each latch hook 28 a, 28 b, the movable members 29 a, 29 b arerotated against the elasticity of the springs 41 a, 41 b. Therefore, theoperating button 31 is pushed by the upper movable member 29 a, and theoperating buttons 32, 33 are pushed by the lower movable member 29 b,respectively.

Therefore, when the AC power source supplies alternating current to theAC circuit part 500, and the DC power source supplies direct current tothe DC circuit part 600, respectively, the AC/DC type microwave oven isoperated.

In the microwave oven according to the first embodiment of the presentinvention, the microswitches 100, 110 detect the opening/closing of thedoor, microcomputer 150 produces the driving signals to the relays 221,222 corresponding to the detected results, and the relays 221, 222 areto open/close the supply of the DC input power source. When themicrowave oven is supplied with large amounts of current from 50A to70A, the microwave oven does not use the microswitches 100, 110 directlyto control the supply of the DC input power source, but use the relays221, 222 capable of not generating the holding of the previous status ofcontacts, instead of the microswitches 100, 110. Therefore, themicrowave can be used more safely.

FIG. 6 is a block diagram of a microwave oven capable of preventingovercurrent of a microswitch for controlling a DC power source accordingto the second embodiment of the present invention. This microwave ovencomprising: a DC/AC converter 300 for converting direct current suppliedby a DC input power source into alternating current, and for supplyingthe converted alternating current to the high voltage transformer;microswitches 100, 110 for openinig/closing a connection between the DCinput power source and the DC/AC converter 300; current dividers 200,210 being connected to the microswitches 100, 110 in parallel, and fordividing a part of current supplied by the microswitches 100, 110 whenthe microswitches 100, 110 are switched on; and a microwave oscillator400 for being driven by an output voltage of the high voltagetransformer, and for generating microwaves. The microswitches 100, 110are operated by the door for opening/closing the cooking chamber. Thecurrent dividers 200, 210 include relays being connected to themicroswitches 100, 110 in parallel, and include resistors beingconnected to the microswitches 100, 110 and/or the relays 200, 210 inseries. The resistors can regulate rates of current through themicroswitches 100, 110 and the relays 200, 210. When overcurrent issupplied to the microswitches 100, 110, the microwave oven is capable ofbeing prevented from the holding of the previous status of contactsaccordingly as a part of overcurrent is consumed by operations of therelays 200, 210.

FIGS. 7a and 7 b are a block diagram and symbols of relays of FIGS. 5and 6, respectively. The relay called an electromagnetic relay has ahinge-type relay and a plunger-type relay, etc. Because thecharacteristic of isolation of the plunger-type relay is excellent, andthe capability of contact is large, the plunger-type relay is used as anelectromagnetic contactor, an electromagnetic switch, and an auxiliaryrelay of power type, etc. In the plunger type relay, a moving-iron ismoving linearly in an electromagnetic coil according to being excited orbeing degaussed by the electromagnetic coil, and a mechanism of contactbeing connected to the moving-iron is opened/closed by using themovement of the moving-iron. The exciting represents flowing current,while the degaussing represents not flowing current. The referencenumeral 9 is a coil, the reference numeral 10 is an independent contact,the reference numeral 11 is a normally open terminal, and the referencenumeral 12 is a normally closed terminal. When current flows through thecoil 9, the coil part becomes an electromagnet to pull the independentcontact 10, and the independent contact 10 is connected to the normallyopen terminal 11 instead of the normally closed terminal 12. Then,current is used for magnetizing the coil 9. As shown in FIG. 7b, contacta 13 means the status of connecting the independent contact 10 to thenormally open terminal 11 when current flows through the coil 9. Contactb 13 means the status of connecting the independent contact 10 to thenormally closed terminal 12 when current is not flowing through the coil9.

FIG. 9 is a schematic diagram of a microwave oven capable of preventingovercurrent of a microswitch for controlling a DC power source accordingto die second embodiment of the present invention. This microwave ovenaccording to the second embodiment comprises an AC circuit part 500, aDC circuit part 600, and a microwave oscillating part 400. The ACcircuit part 500 supplies a high voltage transformer 410 withalternating current by an AC input power source, and the DC circuit part600 supplies to the high voltage transformer 410 which convertsalternating current after converting direct current supplied by a DCinput power source into alternating current, and the microwaveoscillating part 400 generates microwaves by means of the outputtingvoltage of the high voltage transformer 410. The operation of the ACcircuit part 500 and the microwave oscillating part 400 are the same asabove-described in the first embodiment. The opening/closing of the DCinput power source in the DC circuit part 600 is accomplished by meansof the microswitches 100, 110. Therefore, this microwave oven canprevent the holding of the previous status of large amounts of currentin the microswitches 100, 110 by using differentiated current dividers201, 211. The microwave oven according to the second embodiment containsthe first relay 201, and the second relay 211 being connected to themicroswitches 100, 110 in parallel. The relays 201, 211 are turned onwhen the microswitches 100, 110 are turned on, respectively.Accordingly, at least a part of current through the microswitches 100,110 is flowing through the relays 201, 211.

Since direct current being supplied by the DC input power source isdivided by the microswitches 100, 110 and the relays 201, 211, theamounts of current through the microswitches 100, 110 can be reduced.Accordingly, the holding of the previous status of contacts in themicroswitches 100, 110 is capable of being prevented, and the operationsof the microswitches 100, 110 are accomplished safely.

The second embodiment according to the present invention, however, usesthe relays 201, 211 which are the means for dividing a part of currentthrough the microswitches 100, 110, and uses a device of a non-contactswitch, etc.

This microwave oven can heat/cook food by using both the DC input powersource and the AC input power source. Then, this microwave oven containsa differentiated selecting switch (not shown) to operate selectively theDC circuit part 600 or the AC circuit 500.

Meanwhile, each resistor 102, 112, 202, 212 is connected to the relays201, 211 and the switches PD, SD in series. This resistors 102, 112,202, 212 are used for current-limiting. As each resistor 102, 112, 202,212 is controlled adequately, the rates of current through themicroswitches 100, 110 and the relays 201, 211 are capable of beingregulated. When the rates of current are regulated by using theresistors 102, 112, 202, 212, the microswitches 100, 110 are capable ofbeing prevented easily from the holding of the previous status ofcontacts.

In the second embodiment, however, according to present invention, thismicrowave oven adapts the relays 201, 211 for preserving the first andsecond microswitches MS1, MS2, and adapts an additional relay forpreserving the third microswitch MS3 as shown in FIG. 2.

As above-described, this microwave oven according to the presentinvention is capable of preventing from the holding of the previousstatus of contacts in the microswitches by being prevented theovercurrent of the microswitches. Accordingly, this microwave oven iscapable of being prevented from faulty operations of the microswitches,and the heating/cooking of the microwave oven is accomplished safely.

While the present invention has been particularly shown and describedwith reference to the preferred embodiment thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be affected therein without departing from the spirit andscope of the invention as defined by the appended claims.

What is claimed is:
 1. A microwave oven having a case forming a cookingchamber, a door for opening/closing said chamber, a high voltagetransformer for generating a high voltage, and a magnetron forgenerating microwaves driven by said high voltage being outputted fromsaid high voltage transformer, the microwave oven comprising: means fordetecting opening/closing of said chamber; means for controlling foroutputting a driving signal corresponding to said detectedopening/closing of said chamber; and means for opening/closing forcontrolling a power source supplied to said high voltage transformeraccording to reception of said driving signal.
 2. The microwave oven asclaimed in claim 1, wherein said means for detecting is a microswitchwhich is a detector for detecting said opening/closing of said cookingchamber.
 3. The microwave oven as claimed in claim 1, wherein said meansfor opening/closing is an electromagnetic relay for controlling anopening/closing of an input power source to open/close a contactaccording to said driving signal.
 4. The microwave oven as claimed inclaim 3, wherein said electromagnetic relay is a relay for controlling asupply of large amounts of current from 50A to 70A.
 5. In a microwaveoven having a case forming a cooking chamber, a door for opening/closingsaid chamber, a high voltage transformer for generating a high voltage,and a magnetron for generating microwaves driven by said high voltagebeing outputted from said high voltage transformer, an interlockingdevice of a microwave oven comprising: microswitches for detectingopening/closing of said chamber; means for controlling for outputting adriving signal corresponding to said detected opening/closing of saidchamber; and a relay for opening/closing for controlling a powersupplied to said high voltage transformer according to reception of saiddriving signal.
 6. The interlocking device of the microwave oven asclaimed in claim 5, wherein said electromagnetic relay is a relay forcontrolling a supply of large amounts of current from 50A to 70A.
 7. Amicrowave oven using microwaves, comprising: a direct current (DC)circuit part for converting direct current supplied by a DC input powersource into alternating current, and for supplying said convertedalternating current; opening/closing means for connecting between saidDC input power source and said DC circuit part; current dividing meansconnected to said opening/closing means for dividing a part of currentsupplied by said opening/closing means when said opening/closing meansis switched on; and microwave oscillating means driven by an outputvoltage of a high voltage transformer for generating microwaves.
 8. Themicrowave oven as claimed in claim 7, wherein said opening/closing meansis a contact type microswitch operated by opening/closing of said door.9. The microwave oven as claimed in claim 7, wherein said currentdividing means is a relay connected in parallel with saidopening/closing means.
 10. The microwave oven as claimed in claim 9,further comprising resistors connected in series with saidopening/closing means and said relay current dividing meansrespectively, for regulating each rate of current through saidopening/closing means and said relay, respectively.
 11. The microwaveoven as claimed in claim 7, wherein said current dividing means is anon-contact switch connected in parallel with said opening/closingmeans.
 12. A device for preventing overcurrent of a microswitch,comprising: a microswitch for opening/closing a connection between adirect current (DC) input power source and a DC circuit part suppliedwith direct current; and current dividing means connected in parallelwith said microswitch for dividing a part of current through saidmicroswitch when said microswitch is switched on.
 13. The device forpreventing overcurrent of a microswitch as claimed in claim 12, whereinsaid current dividing means is a relay connected in parallel with saidmicroswitch.
 14. The device for preventing overcurrent of a microswitchas claimed in claim 13, further comprising resistors connected in serieswith said microswitch and said relay current dividing means,respectively, for regulating each rate of current through saidmicroswitch and said relay, respectively.